Semiconductor integrated circuits (IC) typically include metallization layers to connect various components of the IC, called interconnect, or back end of line (BEOL) elements. These metal layers are typically formed from copper or aluminum.
One known technique for forming copper interconnects on an IC is known as additive patterning, sometimes called a damascene process, which refers to traditional metal inlaying techniques. A so-called damascene process may include patterning dielectric materials, such as silicon dioxide, or fluorosilicate glass (FSG), or organo-silicate glass (OSG) with open trenches where the copper or other metal conductors should be. A copper diffusion barrier layer (typically Ta, TaN, or a bi-layer of both) is deposited, followed by a deposited copper seed layer, followed by a bulk Copper fill, e.g., using an electro-chemical plating process. A chemical-mechanical planarization (CMP) process may then be used to remove any excessive copper and barrier, and may thus be referred to as a copper CMP process. The copper remaining in the trench functions as a conductor. A dielectric barrier layer, e.g., SiN or SiC, is then typically deposited over the wafer to prevent copper corrosion and improve device reliability.
With more features being packed into individual semiconductor chips, there is an increased need to pack passive components, such as resistors, into the circuits. Some resistors can be created through ion implantation and diffusion, such as poly resistors. However, such resistors typically have high variations in resistance value, and may also have resistance values that change drastically as a function of temperature. A new way to construct integrated resistors, called Thin-Film Resistors (TFRs) has been introduced in the industry to improve integrated resistor performance. Known TFRs are typically formed from SiCr (silicon-chromium), SiCCr (silicon-silicon carbide-chromium), TaN (tantalum nitride), NiCr (nickel-chromium), AlNiCr (aluminum-doped nickel-chromium), or TiNiCr (titanium-nickel-chromium), for example
Most typical TFR construction methods utilize two or more additional photomasks, which adds cost to the manufacturing process. In addition, some TFRs are not compatible with interconnects formed from particular metals. For example, some TFRs or TFR manufacturing methods are not compatible with copper interconnects, while other TFRs or TFR manufacturing methods are not compatible with aluminum interconnects.
FIG. 1 shows a cross-sectional view of two example TFRs 10A and 10B devices implemented using conventional processes, which typically require three added mask layers. A first added mask layer is used to create the TFR heads 12A and 12B. A second added mask layer is used to create the TFRs 14A and 14B. A third added mask layer is used to create TFR vias 16A and 16B. As shown, TFRs 12A and 12B are formed across the top and bottom of TFR heads 12A and 12B, respectively, but in each case three added mask layers are typically required.
FIG. 2 shows a cross-sectional view of a known IC structure including an example TFR 30 formed in view of the teachings of U.S. Pat. No. 9,679,844, wherein TFR 30 can be created using a single added mask layer and damascene process, for copper back-end-of-line (BEOL) connection. A TFR film 34, in this example a SiCCr film, may be deposited into trenches patterned into a previously processed semiconductor substrate. As shown, SiCCr film 34 is constructed as a resistor between conductive (e.g., copper) TFR heads 32, with an overlying dielectric region including a dielectric layer 36 (e.g., SiN or SiC) and a dielectric cap region 38 (e.g., SiO2) formed over the SiCCr film 34. The IC structure including TFR 30 may be further processed for a typical Cu (copper) interconnect process (BEOL), e.g., next level of via and trench. TFR 30 may be connected with other parts of the circuit using typical copper vias 40 connected to the copper TFR heads 32 for example.